Effect of Brackish Water Irrigation on Cotton Growth and Yield Based on Multi-method Comprehensive Evaluation

Abstract

In order to explore the effects of different concentrations of brackish water irrigation on the growth and yield of cotton, clarify the appropriate threshold of brackish water irrigation for cotton, and alleviate the shortage of fresh water resources and the problem of brackish water utilization in cotton areas, five brackish water irrigation gradients were set up in this study. The agronomic traits such as plant height, leaf area, number of fruit branches and yield components such as single boll weight, number of bolls per plant and seed cotton yield were systematically measured. Combined with three evaluation methods of entropy weight-TOPSIS, grey correlation analysis and principal component analysis, the growth and production performance of cotton under different brackish water treatments were comprehensively quantified in multiple dimensions. The results showed that the salt stress of brackish water had a significant gradient inhibitory effect on the vegetative growth and reproductive growth of cotton. With the increase of irrigation water salinity, the plant height, leaf area and fruit branch number of cotton showed a continuous downward trend. Among them, leaf area was the most sensitive to salt stress, which was the core dominant index affecting the comprehensive growth of cotton. Compared with the clear water control, the photosynthetic organ formation and reproductive growth of cotton treated with high concentration of brackish water were inhibited, and the single boll weight and the number of bolls per plant were significantly reduced, resulting in a significant reduction in seed cotton yield. The yield of T4 treatment was 24.19 % lower than that of CK. The order of the three evaluation models was highly consistent, which was CK > T1 > T2 > T3 > T4. The traits and yield of cotton treated with low salt T1 only decreased slightly, and the yield reduction was only 3.17 %, which could maintain a high production level. In summary, mild brackish water irrigation has little effect on cotton production and can be popularized and applied in saline water-deficient cotton areas, while medium and high concentrations of brackish water stress will significantly inhibit cotton growth and reduce production capacity, which should be strictly avoided in production. This study can provide theoretical basis and technical support for the safe and efficient utilization of brackish water resources in cotton fields and the stable and high-yield cultivation of cotton.